Which timer instruction energizes its DN bit after its accumulated value is equal to its preset value?

The Timer On Delay instruction is specifically designed to initiate an output after a certain duration has elapsed, allowing for a defined delay before the output is energized. This instruction keeps track of the elapsed time and only sets the Done (DN) bit when the accumulated time reaches the preset value. As such, the DN bit serves as an indicator that the timer has completed its designated timing interval.

In contrast, other types of timers have different functionalities. For instance, the Timer Off Delay instruction operates by maintaining the output for a specified time after the input has been turned off. The Retentive Timer is designed to retain its accumulated time even when the condition that initiated the timing is no longer active, which can lead to different behaviors regarding the DN bit. Finally, the Non-retentive Timer resets the accumulated value to zero once the applicable input condition is no longer true, meaning it does not hold value across cycles like retentive timers.

Thus, the Timer On Delay clearly aligns with the scenario presented in the question, where the output is energized after the accumulated value matches the preset value.